With the development of tumor radiology and material science, radiotherapy has gradually entered the age of “three precisions” comprising precise positioning, precise planning and precise therapy as an important means for treating cancers. When the rotating plane of a main frame is set to be perpendicular to the horizontal plane, the rotating plane is an X plane, its rotating axis at the moment is defined as a Z axis, the horizontal straight line perpendicular to and cross with the Z axis is an X axis, and the straight line perpendicular to and cross with the Z axis and the X axis respectively is a Y axis. The Z axis and the Y axis define a Y plane, the Y axis and the X axis define an X plane, and the Z axis and the X axis define a horizontal plane (Z plane). The present medical linear accelerator (radiotherapy equipment) is driven by rotation of the main frame to rotate in the X plane or a plane parallel to the X plane, the accelerator follows the main frame to rotate, and the central axis of rays emitted by the accelerator is perpendicular to the rotating axis of the main frame and is intersected with the rotating axis at a point, i.e., an isocenter. Generally, during therapy, the lesion of a patient is put at the isocenter, the main frame is rotated, the accelerator rotates around the lesion in the X plane or the plane parallel to the X plane, and thus rays irradiate the lesion from different directions to better kill sick cells. However, both the patient and the lesion have a three-dimensional size, and the present therapy equipment can only irradiate 360° from one planar space, but cannot irradiate a three-dimensional spherical space. Thus, a so-called accelerator nodding device is emerged, which is mainly characterized in that the main frame is suspended on two struts via a rotating shaft on the X axis, and a driving device drives the main frame to rotate around the X axis; the main frame and the accelerator are very heavy, and the torque borne by the rotating shaft is very large, so the requirement for the driving device is very high.